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The innermost region of the Milky Way harbors the central molecular zone (CMZ). This region contains a large amount of molecular gas but a poor star formation rate considering the densities achieved by the gas in this region. We used the arepo code to perform a hydrodynamic and star formation simulation of the Galaxy, where a Ferrers bar was adiabatically introduced. During the stage of bar imposition, the bar strength excites density waves close to the inner Lindblad resonance guiding material toward the inner Galaxy, driving the formation of a ring that we qualitatively associate with the CMZ. During the simulation, we identified that the ring passes three main phases, namely: formation, instability, and quasi-stationary stages. During the whole evolution, and particularly in the quasi-stationary stage, we observe that the ring is associated with the x2 family of periodic orbits. Additionally, we found that most of the star formation occurs during the ring formation stage, while it drastically decreases in the instability stage. Finally, we found that when the gas has settled in a stable x2 orbit, the star formation takes place mostly after the dense gas passes the apocenter, triggering the conveyor-belt mechanism described in previous studies., Comment: Submitted to PASA

Computer science has historically presented barriers for non-native English speaking (NNES) students, often due to language and terminology challenges. With the rise of large language models (LLMs), there is potential to leverage this technology to support NNES students more effectively. Recent implementations of LLMs as tutors in classrooms have shown promising results. In this study, we deployed an LLM tutor in an accelerated introductory computing course to evaluate its effectiveness specifically for NNES students. Key insights for LLM tutor use are as follows: NNES students signed up for the LLM tutor at a similar rate to native English speakers (NES); NNES students used the system at a lower rate than NES students -- to a small effect; NNES students asked significantly more questions in languages other than English compared to NES students, with many of the questions being multilingual by incorporating English programming keywords. Results for views of the LLM tutor are as follows: both NNES and NES students appreciated the LLM tutor for its accessibility, conversational style, and the guardrails put in place to guide users to answers rather than directly providing solutions; NNES students highlighted its approachability as they did not need to communicate in perfect English; NNES students rated help-seeking preferences of online resources higher than NES students; Many NNES students were unfamiliar with computing terminology in their native languages. These results suggest that LLM tutors can be a valuable resource for NNES students in computing, providing tailored support that enhances their learning experience and overcomes language barriers.

The long-term evolution of the outer Solar System is subject to the influence of the giant planets, however, perturbations from other massive bodies located in the region imprint secular signatures, that are discernible in long-term simulations. In this work, we performed an in-depth analysis of the evolution of massive objects Eris, 2015 KH$_{162}$, Pluto, and 2010 EK$_{139}$ (a.k.a. Dziewanna), subject to perturbations from the giant planets and the 34 largest trans-Neptunian objects. We do this by analysing 200, 1 Gyr long simulations with identical initial conditions, but requiring the numerical integrator to take different time steps for each realization. Despite the integrator's robustness, each run's results are surprisingly different, showing the limitations of individual realizations when studying the trans-Neptunian region due to its intrinsic chaotic nature. For each object, we find orbital variables with well-defined oscillations and limits, and others with surprisingly large variances and seemingly erratic behaviors. We found that 2015 KH$_{162}$ is a non-resonant and very stable object that experiences only limited orbital excursions. Pluto is even more stable and we found a new underlying constraining mechanism for its orbit; 2010 EK$_{139}$ is not well trapped in the 7:2 mean motion resonance in the long-term and cannot be trapped simultaneously in von-Zeipel-Lidov-Kozai resonance; and finally, we found that at present Eris's longitude of perihelion is stationary, tightly librating around 190$^\circ$, but unexpectedly loses its confinement, drifting away after 150 Myr, suggesting a missing element in our model., Comment: 23 pages, 12 figures. Accepted for publication in the AJ

Characterizing the dimensionality of the superconducting state in the infinite-layer (IL) nickelates is crucial to understand its nature. Most studies have addressed the problem by studying the anisotropy of the upper critical fields. Yet, the dominance of Pauli-paramagnetism effects over orbital ones makes it challenging to interpret the experiments in terms of dimensionality. Here we address the question from a different perspective, by investigating the vortex phase diagram in the mixed-state. We demonstrate that superconducting Pr0.8Sr0.2NiO2 thin films present a vortex liquid-to-glass transition of a purely two-dimensional nature. The obtained results suggest that bidimensionality is an intrinsic property, and that superconductivity resides in fully-decoupled NiO2 planes. In this scenario, the coherence length along the c-axis must be shorter than the distance between those planes, while Josephson and magnetostatic coupling between them must be negligible. We believe that these conclusions are relevant for theories on the origin of superconductivity in the IL-nickelates.

We investigate the quantum geometric tensor, which is comprised of the Berry curvature and quantum metric, in a generalized Dirac two-band system with non-integer dispersion, $E(\mathbf{k})\sim k^{\alpha}$. Our analysis reveals that this type of dispersion introduces significant and novel effects on band geometry and topology. We calculate the Berry curvature and observe its redistribution in momentum space as $\alpha$ varies. Notably, despite this redistribution, the change in Chern number across topological transitions remains quantized as an integer, even for non-integer $\alpha$. We illustrate the physical implications of this redistribution by computing the orbital magnetization. Furthermore, we demonstrate that the Berry curvature and quantum metric can become concentrated and even diverge in regions of momentum space where the energy band exhibits high curvature or non-analytic behavior. While it is well established that Berry curvature monopoles form at band touchings, our findings indicate that they can also emerge at sharp band corners, even in the absence of band touchings., Comment: 6 pages, 3 figures

Stars presently identified in the bulge spheroid are probably very old, and their abundances can be interpreted as due to the fast chemical enrichment of the early Galactic bulge. The abundances of the iron-peak elements are important tracers of nucleosynthesis processes, in particular oxygen burning, silicon burning, the weak s-process, and alpha-rich freeze-out. Aims. The aim of this work is to derive the abundances of V, Cr, Mn, Co, Ni, and Cu in 58 bulge spheroid stars and to compare them with the results of a previous analysis of data from APOGEE. We selected the best lines for V, Cr, Mn, Co, Ni, and Cu located within the H-band of the spectrum, identifying the most suitable ones for abundance determination, and discarding severe blends. Using the stellar physical parameters available for our sample from the DR17 release of the APOGEE project, we derived the individual abundances through spectrum synthesis. We then complemented these measurements with similar results from different bulge field and globular cluster stars, in order to define the trends of the individual elements and compare with the results of chemical-evolution models. We verify that the H-band has useful lines for the derivation of the elements V, Cr, Mn, Co, Ni, and Cu in moderately metal-poor stars. The resulting abundances indicate that: V, Cr, and Ni vary in lockstep with Fe; Co tends to vary in lockstep with Fe, but could be showing a slight decrease with decreasing metallicity; and Mn and Cu decrease with decreasing metallicity. These behaviours are well reproduced by chemical-evolution models except for Cu, which appears to drop faster than the models predict for moderate metallicities. Finally, abundance indicators combined with kinematical and dynamical criteria appear to show that our 58 sample stars are likely to have originated in situ., Comment: 12 pages, Astronomy & Astrophysics, accepted on 9/October/2024

The sound modes of a flowing superfluid is described by the massless Klein-Gordon equation in an effective background metric. This effective background metric can be designed to mimick a black hole using the acoustic horizon. In this work, we study the AdS/CFT dual of the sound modes in the presence of an acoustic horizon in the bulk. Focusing on fluids with a purely radial flow, we derive the metric tensor for the effective acoustic spacetime and deduce a necessary condition for an acoustic black hole geometry to exist within the fluid. Using specific examples of superfluid velocity profiles, we obtained the source, operator expectation value, Green's function, and spectral density of the dual field theory by solving for the asymptotic behavior of the sound modes near the AdS boundary. In all our examples, the sound modes remain gapless but the excitations are described by branch cuts, instead of poles, which is typical of strongly coupled systems. Furthermore, we calculate the effective Hawking temperature of the dual field theory associated with the bulk acoustic horizon. Lastly, we investigate the near horizon properties and derive the superfluid velocity profile that can give rise to an infrared emergent quantum criticality., Comment: 10 pages, 4 figures

In order to solve problems of practical importance, quantum computers will likely need to incorporate quantum error correction, where a logical qubit is redundantly encoded in many noisy physical qubits. The large physical-qubit overhead typically associated with error correction motivates the search for more hardware-efficient approaches. Here, using a microfabricated superconducting quantum circuit, we realize a logical qubit memory formed from the concatenation of encoded bosonic cat qubits with an outer repetition code of distance $d=5$. The bosonic cat qubits are passively protected against bit flips using a stabilizing circuit. Cat-qubit phase-flip errors are corrected by the repetition code which uses ancilla transmons for syndrome measurement. We realize a noise-biased CX gate which ensures bit-flip error suppression is maintained during error correction. We study the performance and scaling of the logical qubit memory, finding that the phase-flip correcting repetition code operates below threshold, with logical phase-flip error decreasing with code distance from $d=3$ to $d=5$. Concurrently, the logical bit-flip error is suppressed with increasing cat-qubit mean photon number. The minimum measured logical error per cycle is on average $1.75(2)\%$ for the distance-3 code sections, and $1.65(3)\%$ for the longer distance-5 code, demonstrating the effectiveness of bit-flip error suppression throughout the error correction cycle. These results, where the intrinsic error suppression of the bosonic encodings allows us to use a hardware-efficient outer error correcting code, indicate that concatenated bosonic codes are a compelling paradigm for reaching fault-tolerant quantum computation., Comment: Comments on the manuscript welcome!

In this work, we analysed young stellar clusters with spatial and kinematic coherence in the Orion star-forming complex. For this study, we selected a sample of pre-main sequence candidates using parallaxes, proper motions and positions on the colour-magnitude diagram. After applying a hierarchical clustering algorithm in the 5D parameter space provided by Gaia DR3, we divided the recovered clusters into two regimes: Big Structures and Small Structures, defined by the number of detected stars per cluster. In the first regime, we found 13 stellar groups distributed along the declination axis in the regions where there is a high density of stars. In the second regime, we recovered 34 clusters classified into two types: 14 as small groups completely independent from the larger structures, including four candidates of new clusters, and 12 classified as sub-structures embedded within five larger clusters. Additionally, radial velocity data from APOGEE-2 and GALAH DR3 was included to study the phase space in some regions of the Orion complex. From the Big Structure regime, we found evidence of a general expansion in the Orion OB1 association over a common centre, giving a clue about the dynamical effects the region is undergoing. Likewise, in the Small Structure regime, the projected kinematics shows the ballistic expansion in the $\lambda$ Orionis association and the detection of likely events of clusters' close encounters in the OB1 association., Comment: 19 pages, 17 figures, 3 tables, accepted in MNRAS

We introduce a class of examples which provide an affine generalization of the nonholonomic problem of a convex body rolling without slipping on the plane. We investigate dynamical aspects of the system such as existence of first integrals, smooth invariant measure and integrability, giving special attention to the cases in which the convex body is a dynamically balanced sphere or a body of revolution., Comment: 29 pages, 8 figures

Researchers in biomedical research, public health, and the life sciences often spend weeks or months discovering, accessing, curating, and integrating data from disparate sources, significantly delaying the onset of actual analysis and innovation. Instead of countless developers creating redundant and inconsistent data pipelines, BioBricks.ai offers a centralized data repository and a suite of developer-friendly tools to simplify access to scientific data. Currently, BioBricks.ai delivers over ninety biological and chemical datasets. It provides a package manager-like system for installing and managing dependencies on data sources. Each 'brick' is a Data Version Control git repository that supports an updateable pipeline for extraction, transformation, and loading data into the BioBricks.ai backend at https://biobricks.ai. Use cases include accelerating data science workflows and facilitating the creation of novel data assets by integrating multiple datasets into unified, harmonized resources. In conclusion, BioBricks.ai offers an opportunity to accelerate access and use of public data through a single open platform., Comment: 23 pages, 2 figures

A central requirement in asymmetric quantum nonlocality protocols, such as quantum steering, is the precise reconstruction of state assemblages -- statistical ensembles of quantum states correlated with remote classical signals. Here we introduce a generalized loss model for assemblage tomography that uses conical optimization techniques combined with maximum likelihood estimation. Using an evidence-based framework based on Akaike's Information Criterion, we demonstrate that our approach excels in the accuracy of reconstructions while accounting for model complexity. In comparison, standard tomographic methods fall short when applied to experimentally relevant data., Comment: 5 + 4 pages, 3 + 3 figures (Main + Supplemental Material)

Long-range frequency hopping spread spectrum (LR-FHSS) is a pivotal advancement in the LoRaWAN protocol that is designed to enhance the network's capacity and robustness, particularly in densely populated environments. Although energy consumption is paramount in LoRaWAN-based end devices, {this is the first study} in the literature, to our knowledge, that models the impact of this novel mechanism on energy consumption. In this article, we provide a comprehensive energy consumption analytical model of LR-FHSS, focusing on three critical metrics: average current consumption, battery lifetime, and energy efficiency of data transmission. The model is based on measurements performed on real hardware in a fully operational LR-FHSS network. While in our evaluation, LR-FHSS can show worse consumption figures than LoRa, we find that with optimal configuration, the battery lifetime of LR-FHSS end devices can reach 2.5 years for a 50 min notification period. For the most energy-efficient payload size, this lifespan can be extended to a theoretical maximum of up to 16 years with a one-day notification interval using a cell-coin battery.

It was recently pointed out that some precise Photon-Galileon couplings in four dimensions (4D) -- inspired by a higher dimensional reduction -- are enough to obtain a Horndeski theory that is less constrained by the stringent experimental bounds on the speed of Gravitational Waves. They imply the constancy of the ratio of speed of gravity to light throughout cosmic evolution. This holds without fine tuning, even if one includes the general $G_4 (\pi,X)$ and $G_5 (\pi)$ scalar potentials. In this paper we go into the details of this 4D Luminal extension of Horndeski theory including its scalar sector. We also present the complete action including the general $G_5(\pi,X),\, G_6(\pi,X)$ scalar potentials. Thus we show all the $U(1)$ gauge invariant vector Galileons in 4D that result from a Kaluza-Klein dimensional reduction from 5D Horndeski. They provide a consistent coupling of a higher derivative vector to scalar modifications of gravity -- namely, without inducing Ostrogradsky ghosts and keeping gauge invariance -- in the aim to explore more universal couplings of dark energy to other matter, such as vectors and in particular the Photon., Comment: 22 pages. Fixed typos, results unchanged. Added references

We explore the Steklov eigenvalue problem on convex polygons, focusing mainly on the inverse Steklov problem. Our primary finding reveals that, for almost all convex polygonal domains, there exist at most finitely many non-congruent domains with the same Steklov spectrum. Moreover, we obtain explicit upper bounds for the maximum number of mutually Steklov isospectral non-congruent polygonal domains. Along the way, we obtain isoperimetric bounds for the Steklov eigenvalues of a convex polygon in terms of the minimal interior angle of the polygon., Comment: 24 pages, 10 figures

We developed SaludConectaMX as a comprehensive system to track and understand the determinants of complications throughout chemotherapy treatment for children with cancer in Mexico. SaludConectaMX is unique in that it integrates patient clinical indicators with social determinants and caregiver mental health, forming a social-clinical perspective of the patient's evolving health trajectory. The system is composed of a web application (for hospital staff) and a mobile application (for family caregivers), providing the opportunity for cooperative patient monitoring in both hospital and home settings. This paper presents the system's preliminary design and usability evaluation results from a 1.5-year pilot study. Our findings indicate that while the hospital web app demonstrates high completion rates and user satisfaction, the family mobile app requires additional improvements for optimal accessibility; statistical and qualitative data analysis illuminate pathways for system improvement. Based on this evidence, we formalize suggestions for health system development in LMICs, which HCI researchers may leverage in future work.

NGC~6558 is a low-galactic latitude globular cluster projected in the direction of the Galactic bulge. Due to high reddening, this region presents challenges in deriving accurate parameters, which require meticulous photometric analysis. We present a combined analysis of near-infrared and optical photometry from multi-epoch high-resolution images collected with Gemini-South/GSAOI+GeMS (in the $J$ and $K_S$ filters) and HST/ACS (in the F606W and F814W filters). We aim to refine the fundamental parameters of NGC~6558, utilizing high-quality Gemini-South/GSAOI and HST/ACS photometries. Additionally, we intend to investigate its role in the formation of the Galactic bulge. We studied the impact of two differential reddening corrections on the age derivation. When removing as much as possible the Galactic bulge field star contamination, the isochrone fitting combined with synthetic colour-magnitude diagrams gives a distance of $8.41^{+0.11}_{-0.10}$ kpc, an age of $13.0\pm 0.9$ Gyr, a reddening of E($B-V$)$\,\,=0.34\pm0.02$, and a total-to-selective coefficient R$_V = 3.2\pm0.2$ thanks to the simultaneous near-infrared$-$Optical synthetic colour-magnitude diagram fitting. The orbital parameters showed that NGC~6558 is confined whitin the inner Galaxy and it is not compatible with a bar-shape orbit, indicating that it is a bulge member. The old age of NGC~6558, combined with similar metallicity and a blue horizontal branch in the Galactic bulge, indicates that it is part of the moderately metal-poor globular clusters. Assembling the old and moderately metal-poor ([Fe/H]$\,\,\sim-1.1$) clusters in the Galactic bulge, we derived their age-metallicity relation with star formation stars at $13.6\pm0.2$ Gyr and effective yields of $\rho=0.007\pm0.009\,\, Z_\odot$ showing a chemical enrichment ten times faster than the ex-situ globular clusters branch., Comment: Accepted for publication in A&A. 14 pages, 12 figures, and 4 tables. The abstract is a reduced version of the accepted one

The electromagnetic properties and microwave absorption capabilities are studied in an anechoic chamber under real radar conditions for mono and bilayer composite samples consisting of a polymeric matrix and a magnetic powder filler, either metallic or ceramic. The effect of the filler type and the filling factor is investigated. The results demonstrate exceptional broadband microwave absorption, making these materials highly suitable for stealth technology applications. The experimentally measured absorptions reach -40 dB, while model-based predictions suggest that these systems could overpass the barrier of -50 dB. The experimental results are supported by models, both for single and bilayer systems.

Scale invariance profoundly influences the dynamics and structure of complex systems, spanning from critical phenomena to network architecture. Here, we propose a precise definition of scale-invariant networks by leveraging the concept of a constant entropy loss rate across scales in a renormalization-group coarse-graining setting. This framework enables us to differentiate between scale-free and scale-invariant networks, revealing distinct characteristics within each class. Furthermore, we offer a comprehensive inventory of genuinely scale-invariant networks, both natural and artificially constructed, demonstrating, e.g., that the human connectome exhibits notable features of scale invariance. Our findings open new avenues for exploring the scale-invariant structural properties crucial in biological and socio-technological systems., Comment: 6 pages, 3 figures and Supplemental Material

Ferroelectrics undergoing spontaneous symmetry breaking can manifest intricate domain patterns that allow the exploration of topological defects and their potential applications, such as domain-wall nanoelectronics. Engineering actual devices remains a challenge as domain patterns have complexity-driven properties whose origin and nature are still obscure. In relaxor ferroelectrics, dominant unconventional behavior, including thermal hysteresis and dielectric dispersion, is believed to result from frustrated dynamics of mesoscopic polar nanoregions (PNRs), where competing interaction terms among multiple components allow emergent phenomena as the result of minimizing conflicts. Existing theories propose analogies with Griffiths' phases or glassy states but fail to provide a full description, making relaxors a paradigm of hereto unexplained non-ergodic phenomenology. Here, we propose an explanatory mechanism based on the competition between intrinsic mesoscopic scales that naturally arise from discrete-inversion-symmetry-breaking and topological charge-screening flux-closure constraints. Computational analysis and experimental results on domain patterns in potassium-lithium-tantalate-niobate (KTN:Li) identify the key role of spontaneous polarization vortices, dependent on the ratio between collinear and non-collinear interactions. Our findings introduce a new perspective on frustration mechanisms, demonstrating how geometrical concepts are a fundamental ingredient in emergent ferroelectric behavior. They also shed light on the physics of ferroelectric topological defects, a possible route to noise-resistant memory and processing mechanisms., Comment: 10 pages, 5 figures and Supplementary Material

We propose to use automatically generated instruction-following data to improve the zero-shot capabilities of a large multimodal model with additional support for generative and image editing tasks. We achieve this by curating a new multimodal instruction-following set using GPT-4V and existing datasets for image generation and editing. Using this instruction set and the existing LLaVA-Finetune instruction set for visual understanding tasks, we produce GenLLaVA, a Generative Large Language and Visual Assistant. GenLLaVA is built through a strategy that combines three types of large pretrained models through instruction finetuning: Mistral for language modeling, SigLIP for image-text matching, and StableDiffusion for text-to-image generation. Our model demonstrates visual understanding capabilities superior to LLaVA and additionally demonstrates competitive results with native multimodal models such as Unified-IO 2, paving the way for building advanced general-purpose visual assistants by effectively re-using existing multimodal models. We open-source our dataset, codebase, and model checkpoints to foster further research and application in this domain., Comment: Add more results using task tokens, expand the introduction and related work FIX: error in LLM-as-judge evaluation that was over-inflating the results

In this paper, we deduce a new multivariate regression model designed to fit correlated binary data. The multivariate distribution is derived from a Bernoulli mixed model with a nonnormal random intercept on the marginal approach. The random effect distribution is assumed to be the generalized log-gamma (GLG) distribution by considering a particular parameter setting. The complement log-log function is specified to lead to strong conjugacy between the response variable and random effect. The new discrete multivariate distribution, named MBerGLG distribution, has location and dispersion parameters. The MBerGLG distribution leads to the MBerGLG regression (MBerGLGR) model, providing an alternative approach to fitting both unbalanced and balanced correlated response binary data. Monte Carlo simulation studies show that its maximum likelihood estimators are unbiased, efficient, and consistent asymptotically. The randomized quantile residuals are performed to identify possible departures from the proposal model and the data and detect atypical subjects. Finally, two applications are presented in the data analysis section.

The renormalization group (RG) constitutes a fundamental framework in modern theoretical physics. It allows the study of many systems showing states with large-scale correlations and their classification in a relatively small set of universality classes. RG is the most powerful tool for investigating organizational scales within dynamic systems. However, the application of RG techniques to complex networks has presented significant challenges, primarily due to the intricate interplay of correlations on multiple scales. Existing approaches have relied on hypotheses involving hidden geometries and based on embedding complex networks into hidden metric spaces. Here, we present a practical overview of the recently introduced Laplacian Renormalization Group for heterogeneous networks. First, we present a brief overview that justifies the use of the Laplacian as a natural extension for well-known field theories to analyze spatial disorder. We then draw an analogy to traditional real-space renormalization group procedures, explaining how the LRG generalizes the concept of "Kadanoff supernodes" as block nodes that span multiple scales. These supernodes help mitigate the effects of cross-scale correlations due to small-world properties. Additionally, we rigorously define the LRG procedure in momentum space in the spirit of Wilson RG. Finally, we show different analyses for the evolution of network properties along the LRG flow following structural changes when the network is properly reduced., Comment: 26 pages, 7 figures. Accepted to be published in JSTAT

In this radiation tolerance study, Low Gain Avalanche Detectors (LGADs) with a carbon-enriched broad and shallow multiplication layer were examined in comparison to identical non-carbonated LGADs. Manufactured at IMB-CNM, the sensors underwent neutron irradiation at the TRIGA reactor in Ljubljana, reaching a fluence of $1.5e^{15} {n_{eq}} cm^{-2}$. The results revealed a smaller deactivation of boron and improved resistance to radiation in carbonated LGADs. The study demonstrated the potential benefits of carbon enrichment in mitigating radiation damage effects, particularly the acceptor removal mechanism, reducing the acceptor removal constant by more than a factor of two. Additionally, time resolution and collected charge degradation due to irradiation were observed, with carbonated samples exhibiting better radiation tolerance. A noise analysis focused on baseline noise and spurious pulses showed the presence of thermal-generated dark counts attributed to a too narrow distance between the gain layer end and the p-stop implant at the periphery of the pad for the characterized LGAD design; however, without significant impact of operation performance.

We present a method for multi-concept customization of pretrained text-to-video (T2V) models. Intuitively, the multi-concept customized video can be derived from the (non-linear) intersection of the video manifolds of the individual concepts, which is not straightforward to find. We hypothesize that sequential and controlled walking towards the intersection of the video manifolds, directed by text prompting, leads to the solution. To do so, we generate the various concepts and their corresponding interactions, sequentially, in an autoregressive manner. Our method can generate videos of multiple custom concepts (subjects, action and background) such as a teddy bear running towards a brown teapot, a dog playing violin and a teddy bear swimming in the ocean. We quantitatively evaluate our method using videoCLIP and DINO scores, in addition to human evaluation. Videos for results presented in this paper can be found at https://github.com/divyakraman/MultiConceptVideo2024., Comment: Paper accepted to AI4CC Workshop at CVPR 2024

We show that the full Horndeski theory with both curvature and torsion can support nonsingular, stable and subluminal cosmological solutions at all times. Thus, with torsion, the usual No-Go theorem that holds in a curved spacetime is avoided. In particular, it is essential to include the nonminimal derivative couplings of the $\mathcal{L}_{5}$ part of the Horndeski action ($G^{\mu\nu}\,\nabla_\mu \nabla_\nu \phi,$ and $(\nabla^2 \phi)^3$). Without the latter a No-Go already impedes the eternal subluminality of nonsingular, stable cosmologies., Comment: 21 pages, 13 Figures. Version accepted for publication in JCAP. Results unchanged. Added references

The application of Horndeski theory/ Galileons for late time cosmology is heavily constrained by the strict coincidence in the speed of propagation of gravitational and electromagnetic waves. These constraints presuppose that the minimally coupled photon is not modified, not even at the scales where General Relativity (GR) may need modification. We find that the 4D Galileon obtained from a Kaluza-Klein compactification of its higher dimensional version is a natural simultaneous modification of GR and electromagnetism with automatically "luminal" gravitational waves. This property follows without any fine tuning of Galileon potentials for a larger class of theories than previously thought. In particular, the $G_4$ potential is not constrained by the speed test and $G_5$ may also be present. In other words, some Galileon models that have been ruled out since the event GW170817 are, in fact, not necessarily constrained if they arise in 4D from compactifications of their higher dimensional Galileon counterparts. Besides their compelling luminality, the resulting vector Galileons are naturally $U(1)$ gauge invariant. We also argue that the Vainshtein screening that allows to recover GR predictions for solar system tests is also at work for electrodynamics in the dense region of laboratory tests., Comment: 5 pages. Matches the version published in PLB. Results unchanged

Quantum states encoded in the time-bin degree of freedom of photons represent a fundamental resource for quantum information protocols. Traditional methods for generating and measuring time-bin encoded quantum states face severe challenges due to optical instabilities, complex setups, and timing resolution requirements. Here, we leverage a robust approach based on Hong-Ou-Mandel interference that allows us to circumvent these issues. First, we perform high-fidelity quantum state tomographies of time-bin qubits with a short temporal separation. Then, we certify intrasystem polarization-time entanglement of single photons through a nonclassicality test. Finally, we propose a robust and scalable protocol to generate and measure high-dimensional time-bin quantum states in a single spatial mode. The protocol promises to enable access to high-dimensional states and tasks that are practically inaccessible with standard schemes, thereby advancing fundamental quantum information science and opening applications in quantum communication.

In the regularity theory of solutions to elliptic partial differential equations often the concept of stability plays the role of a sufficient condition for smoothness. It is a natural question to ask if this holds true for nonstable but finite Morse index solutions. We provide a negative answer showing the existence of sequences of solutions with radial Morse index equal to 1 for which regularity estimates can not be satisfied., Comment: 8 pages

Starting from a plausible assumption about the Total Revenue concept, a system of economic agents, that simulates the exchange of goods, is studied. Following a methodology equivalent to that used in the statistical-mechanical determination of the distribution of energies in a physical system, it is shown that the price of the exchanged goods arises naturally, as well as the well-known ``Law of demand". It is also shown that by using Euler's Theorem of homogeneous functions, the conditions emerge for the appearance of wholesale and retail prices. We found also that the Total Revenue is the product of two factors: the configurational entropy and a "free energy" type one. We study numerically the case in which the exchanged good is money itself, in systems in which economic agents have a "roof" on the amount of money they can possess. It is shown numerically that the increase in the quantity of money in the hands of the agents necessarily leads to its depreciation, and only the expansion of the economy, understood here as raising the "roof", minimizes this loss of purchasing power. The concept of indexing is discussed., Comment: 19 pages and 10 figures

The optical response of quasi-one-dimensional systems is often dominated by tightly bound excitons, that significantly influence their basic electronic properties. Despite their importance for device performance, accurately predicting their excitonic effects typically requires computationally demanding many-body approaches. Here, we present a simplified model to describe the static macroscopic dielectric function, which depends only on the width of the quasi-one-dimensional system and its polarizability per unit length. We show that at certain interaction distances, the screened Coulomb potential is greater than its bare counterpart, which results from the enhanced repulsive electron-electron interactions. As a test case, we study fourteen different nanoribbons, twelve of them armchair graphene nanoribbons of different families. Initially, we devised a simplified equation to estimate the exciton binding energy and extension that provides results comparable to those from the full Bethe-Salpeter equation, albeit for a specific nanoribbon family. Then, we used our proposed screening potential to solve the 1D Wannier-Mott equation, which turn out to be broad approach, that is able to predict binding energies that match quite well the ones obtained with the Bethe-Salpeter equation, irrespective of the nanoribbon family.

Low-disorder two-dimensional electron systems in the presence of a strong, perpendicular magnetic field terminate at very small Landau level filling factors in a Wigner crystal (WC), where the electrons form an ordered array to minimize the Coulomb repulsion. The nature of this exotic, many-body, quantum phase is yet to be fully understood and experimentally revealed. Here we probe one of WC's most fundamental parameters, namely the energy gap that determines its low-temperature conductivity, in record-mobility, ultra-high-purity, two-dimensional electrons confined to GaAs quantum wells. The WC domains in these samples contain $\simeq$ 1000 electrons. The measured gaps are a factor of three larger than previously reported for lower quality samples, and agree remarkably well with values predicted for the lowest-energy, intrinsic, hyper-corelated bubble defects in a WC made of flux-electron composite fermions, rather than bare electrons. The agreement is particularly noteworthy, given that the calculations are done for disorder-free composite fermion WCs, and there are no adjustable parameters. The results reflect the exceptionally high quality of the samples, and suggest that composite fermion WCs are indeed more stable compared to their electron counterparts.